Method of coating a flexible web

ABSTRACT

A method of applying a uniform coating of a soft, pliant material or the like, e.g. wax, on a continuous flexible web to coat a surface of the web with minute quantities of the pliant material. The coating is carried out by placing the web in surface contact with a coating roll made from the pliant material. The web is moved and the roll is turned such that there is a speed differential, i.e. slip, between the contacting surfaces of the roll and the web. The movement of the web over the peripheral surface of the roll in this manner uniformly coats the web with minute amounts of material transferred to the web from the roll surface.

United States Patent 1151 3,66 1,626 Wosaba, II May 9, 1972 54] METHOD OF COATING A FLEXIBLE 257,761 5/1882 Ridgway ..118/77 x WEB 1,351,408 8/1920 Werner... ..118/77 1,768,895 7/1930 Dunn ..118/77 Inventor: Charles Wosaba, ll, sprmgfield 2,014,127 9/1935 Coley et a1. ..118/78 x Townshlmflamllwn s/D 3,319,012 5/1967 Reed eta] ..179/1002 73 Assi nee: The Procter & Gamble Com an Cincin- 1 g nafi Ohio p Primary E.\'aminer--Alfred L. Leavitt Assistant E.\'aminerl(enneth P. Glynn Flledi y 1970 Attorney-Fredrick B. Braun and John V. German [21] Appl. No.: 35,783 ABSTRACT [52 U.S.Cl. ..117/111H 117 1310. 1 117/111R A methbd applying a coating 3 pliant 1 {7/120 1 17/168 1 l8/77 material or the like, e.g. wax, on a continuous flexible web to [51] lm Cl Bose 1/06 C09d3/44 BOSC l 1/00 coat a surface of the web with minute quantities of the pliant [58] 1 l I 1 l R 1 F l l I H material. The coating is carried out by placing the web in surl 17/ 6 l8/76 77 face contact with a coating roll made from the pliant material. The web is moved and the roll is turned such that there is a speed differential, i.e. slip, between the contacting surfaces of [56] Reierences cued the roll and the web. The movement of the web over the UNITED STATES PATENTS peripheral surface of the roll in this manner uniformly coats the web with minute amounts of material transferred to the 2,565,036 8/1951 MacDonald ..117/111 X bf the m||Surface 2,352,658 7/1944 Richmond et al.. ...1l7/111 F 2,987,034 6/ 1961 Redmond ..1 18/78 4 Claims, 1 Drawing Figure H X IO 1 B A 7 (lg-..1 13 q Patented May 9, 1972 INVENTOR. Charles L. Wosobo 11 ATTORNEY BACKGROUND OF THE INVENTION The invention relates to a method of coating a flexible web and, more particularly, to a method of applying small or minute quantities of additive materials to the surface of a continuously moving web.

.1 he coating of small amounts of pliant or waxy materials to the surface of a flexible web such as paper, cloth, nonwoven materials or the like has been attempted in numerous ways none of which have been entirely effective at high speeds in uniformly transferring small, minute quantities over the entire width of the web. One of the more common methods that have been employed in the past has been the pressing of a bar of wax or other pliant material against a surface of the web as it is moved at high speed. It has been found that such a coating technique is only effective for such a relatively short period of time that it is not feasible from a practical standpoint. The major drawback to this prior coating process is that eventually there is a build up of individual fibers from the web on the leading edge of the bar of waxy or pliant material. This results in a loss of contact between the web and the pliant material and consequently transfer is virtually eliminated.

SUMMARY OF THE INVENTION The nature and substance of the present invention will be more readily appreciated after giving consideration to its major aims and purposes. The principal objects of the invention are set forth in the ensuing paragraphs in order to provide a better appreciation of its important aspects prior to describing the details of a preferred embodiment in later portions of this description.

A major object of the invention is the provision of a method of coating a flexible web in order to transfer relatively small or minute quantities of a waxy or other pliant material uniformly over the entire surface of the web on one side.

Another object of the invention is the provision of a method of the above character which can be carried out at high speeds so that the web can be used immediately in a converting machine, if desired, without any effect in the speed of the converting operation.

A further object of a preferred form of the invention is the provision of a method as described above which can be used in the coating of a web of nonwoven material with a waxy or pliant material in order to inhibit rub-off of binder material on the converting equipment with its attendant reduction in the effectiveness and efficiency of the converting operation.

These and other objects are achieved by the provision of a method of coating a flexible web of material which includes the steps of placing the moving web in surface contact with a roll having a surface made from the waxy or pliant material to be coated on the web. Rotation is imparted to the roll so that its surface is moved in relation to the movement of the web thereover. A predetermined amount of slip (speed differential between the web and the roll surface) causes uniform frictional transfer of small or minute amounts of pliant material from the roll surface to the contacting web surface.

BRIEF DESCRIPTION OF THE DRAWING While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter regarded as forming the present invention, it is believed the invention will be better understood from the following description taken in connection with the accompanying drawing in which:

The drawing is a schematic illustration in elevation of the components used in the practice of the method of the invention including a transfer roll shown both in new and in worn condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention is particularly useful in the transfer of pliant or soft waxy materials having lubricating properties to the surface of a moving web which may be any of several flexible materials having a porous surface. The pliant or soft waxy material is preferably a paraffin wax and will be referred to as such in the ensuing description. It will be understood, however, that the invention is not limited to the transfer of paraffin wax. It can be practiced with equally good results in the transfer of any pliant or soft waxy material which may include a lanolin base material or a fabric softener or any other material having the requisite frictional properties that would make it particularly adaptable to the transfer of minute quantities of material from the surface of a coating roll to that of a moving web. In some cases, it may even be desirable to dissolve or suspend other coating materials in the paraffin wax which would then have the additional function of a carrier.

On the other hand, the web of material to which the paraffin wax is transferred is preferably a nonwoven material although the invention is not necessarily limited to that particular material. It can be practiced with equal facility in the transfer of paraffin wax to a paper web, a cloth web or any other material of that general nature that is relatively flexible and somewhat porous so that soft waxy materials can be readily transferred thereto.

In a preferred practice of the method, the flexible web 10 (see drawing) is withdrawn from a tension controller (not shown) and passes over an idler 11 which is suitably supported on the machine frame 12. The coating roll 13 is also supported on the machine frame 12 such that the flexible web 10 is in surface contact with its periphery throughout the angle A (the angle of wrap) shown in the drawing. The flexible web 10 passes downwardly to a converter (not shown) there being a second idler 14 used to guide the web 10 as the coating roll 13 is worn down from its original diameter illustrated in the drawing to its fully worn diameter as illustrated by the broken circular line 15.

The coating roll is preferably made such that its outer core 'is primarily a paraffin wax having a melting point of from about F. to about F. The transfer of paraffin wax material from the surface of the coating roll 13 to the surface 16 of the web 10 occurs as the web 10 makes peripheral contact with and passes over the coating roll 13. The process can be carried outwith web'speeds in excess of 500 f.p.m.

In order to effectively carry out the coating process, it is desirable that a certain amount of slip be present between the surface 16 of the web 10 and the peripheral surface of the coating roll 13. This can be accomplished by merely mounting the coating roll 13 for free rotation such that the movement of the web 10 imparts rotation to the roll 13 inasmuch as it is in driving contact therewith. In such circumstances, a certain amount of slip will inherently be present depending upon the tension in the web 10, the friction in the supporting bearings for the coating roll 13, etc. This will cause the transfer of a minute quantity of paraffin wax material from the roll surface to the web surface 16.

Preferably, however, the amount of slip between the peripheral surface of the roll 13 and the web 10 is controlled so that a predetermined amount of paraffin wax is transferred. This is effected by providing the roll 13 with a positive drive such that its peripheral surface turns at a given differential speed with respect to the speed of the moving web 10. This can be accomplished very effectively with the peripheral surface of the roll 13 running either faster or slower than the speed of the web 10, although preferably it is run slower than the web. An effective mode of accomplishing such drive of the roll 13 is by the provision of a conventional commercially available variable speed drive which permits the operator to adjust the angular speed of the coating roll 13 to achieve the desired amount of slip relative to the movement of the web 10. Once the angular speed has been attained to achieve the desired amount of paraffin wax transfer, the angular speed of the coating roll 13 is preferably maintained constant relative to the web speed.

The amount of paraffin wax transfer from the coating roll 13 to the surface 16 of the flexible web 10 has been found to be dependent upon a number of factors. One of the factors is the degree of wrap represented by the angle A in the drawing. it will be apparent from inspecting the drawing that the degree of wrap diminishes as the coating roll 13 wears from its original size down to its fully worn diameter as represented by the numeral 15. In so doing, the original degree of wrap represented by the angle A is similarly diminished to an angle B as shown in the drawing. Normally, this reduction in the degree of wrap will diminish the amount of paraffin wax transferred to the web 10.

It has been found, however, that the amount of paraffin wax material transferred from the coating roll 13 can be maintained approximately constant as the degree of wrap diminishes for a preferred wax having a melting point of 135 F. available from ARCO Chemical Co. as wax No. 175. it will be appreciated that as the roll 13 diminishes in diameter, its peripheral surface speed will be reduced if the roll 15 is continually driven at a constant angular speed. The reduction in peripheral surface speed of the reduced diameter coating roll 15 provides a greater amount of slip between the peripheral surface of the coating roll 15 and the surface 16 of the web 10. The greater speed differential or higher slip, because of the reduced diameter of coating roll 13, compensates for the simultaneous reduction in degree of wrap so that when carrying out the method in the manner shown in the drawing the amount of transfer of paraffin wax material remains approximately constant as the coating roll diminishes in size if the coating roll is driven at a constant angular speed.

With softer wax materials having a lower melting point, it may be necessary to adjust the angular speed of the coating roll 13 as it decreases in diameter. However, the need for and the number of adjustments is minimal because of the geometry of the arrangement shown in the drawing whereby as the coating roll 13 diameter decreases, the decreased angle of wrap is compensated by an increase in slip for a constant angular velocity of the coating roll 13.

Other factors affecting the transfer of paraffin wax material from the coating roll 13 to the web 10 are such variables as the tension in the web 10, the hardness of the coating roll 13 as well as the smoothness of the web 10 and the finish on the surface of the roll 15. Still another variable that can be used in controlling the amount of wax transfer is skewing of the roll, that is placing its axis at an angle with respect to the path of movement of the web.

EXAMPLE I melting point of 123 F. manufactured by the ARCO Chemical Company and identified by their Code No. 131. The web 10 was 15 inches wide and was passed over a inch diameter coating roll 13 at a speed of 250 f.p.m. while the coating roll 13 was rotated in the same direction at 169 r.p.m. so that its peripheral speed was 221 f.p.m. The web was passed over the coating roll 13 until it was worn down to a diameter of 1% inches. The original angle of wrap was and the final angle of wrap was 66. The web 10 was uniformly coated over its entire width with 0.018 gram per square yard of the paraffin wax from the coating roll.

EXAMPLE II F. as manufactured by ARCO Chemical Company and identified by their Code No. 175. The web 10 was uniformly coated over its entire width with 0.0086 gram per square yard.

EXAMPLE Ill The method was carried out under the same conditions specified in Example 1 except that the coating roll was rotated at a speed of 184 r.p.m. so that its peripheral speed was 241 f.p.m. The web was uniformly coated over its entire width with 0.0072 gram per square yard of the paraffin wax from the coating roll.

While particular embodiments of the invention have been illustrated and described, it will be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention and it is intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

What is claimed as new is:

1. A method of coating a flexible web comprising the steps of:

' a. placing a web in surface contact with a transfer roll having an outer core containing the material to be coated on 0 said web, g

b. moving said web while in surface contact with said transfer roll,

0. controlling the angular speed of the transfer roll thereby controlling the amount of slip between the peripheral contacting surface of said transfer roll and said web and controlling the rate of transfer of the material from the roll peripheral surface to the web surface,

d. decreasing the degree of wrap between the transfer roll and the web as the transfer roll wears to a smaller diameter, and maintaining the angular speed of the transfer roll substantially constant as the degree of wrap decreases to decrease the slip between the contacting surfaces and thereby compensate for reductions in the degree of wrap, and maintaining substantially uniform transfer of material to said web as the degree of wrap decreases.

2. A method of coating as claimed in claim 1 including the step of passing a flexible web of nonwoven material over the transfer roll surface.

3. A method of coating a flexible web as claimed in claim 1 including the step of providing a transfer roll made from paraffin wax.

4. A method of coating as claimed in claim 1 including the steps of passing a flexible web of nonwoven material over the transfer roll surface and providing a transfer roll made from paraffin wax. 

2. A method of coating as claimed in claim 1 including the step of passing a flexible web of nonwoven material over the transfer roll surface.
 3. A method of coating a flexible web as claimed in claim 1 including the step of providing a transfer roll made from paraffin wax.
 4. A method of coating as claimed in claim 1 including the steps of passing a flexible web of nonwoven material over the transfer roll surface and providing a transfer roll made from paraffin wax. 